This project is designed to use a non-invasive imaging technique to improve the accuracy of the clinical diagnosis of dementia of the Alzheimer's type (DAT). While imaging techniques are currently being used to exclude other causes of dementia, this project will evaluate the role of magnetic resonance (MR)-based volume measurements of the temporal lobe in improving the clinical diagnosis. The study will draw upon two resources of the Mayo Clinic: the Mayo Clinic Alzheimer's Disease Patient Registry (ADPR) and an MR-based measurement technique developed at Mayo to measure the volumes the anterior temporal lobe (ATL), medial temporal lobe (MTL), and hippocampal formation (HF). The Mayo Clinic ADPR has been enrolling patients and control subjects for four years and consequently has a mechanism in place to evaluate and diagnose patients for the current project. The MR-volume technique has been developed and its accuracy and reproducibility validated. The present study proposes to apply this technique to 3 groups: patients with DAT, a group of mildly impaired patients, and a group of age, sex, and education matched control subjects to determine if MR can differentiate among the groups on the basis of volumetric measures of the ATL, MTL, and HF. The study will also evaluate the relationships among age, memory function, and severity of dementia (if appropriate) within the three groups. The project will extend over three years and will involve a total of 75 DAT patients, 36 mildly impaired patients, and Ill appropriately matched control subjects. We anticipate that MR measurements of the ATL, MTL, and in particular,, the HF will discriminate between patients with DAT and control subjects in a sensitive and specific fashion. In addition, we anticipate that the ATL, MTL, and in particular, the HF will decrease in volume with age but that the decline will be most pronounced for patients with DAT. Similarly, the volume of the temporal lobe structures, in particular the HF, will correlate directly with clinical indices of memory function in all three groups and in the DAT group will correlate inversely with dementia severity. In sum, we are proposing that measurement of volumetric indices of temporal lobe structures will be a sensitive and specific method of non-invasively distinguishing among patients with DAT, mild cognitive impairment, and normal elderly individuals.